Warmer drawers of conventional design are typically configured as closed boxes, having a construction of single walled or a double walled with insulation or air in between and a sliding drawer of some sort to open up the interior of the box. Such conventional warmer drawers often have front door(s) fixed in a vertical plane and heating of the interior has been by a single cal rod (i.e. sheathed heating element) that will radiate heat, thus warming the interior of the box.
The conventional warmer drawers use mechanical controls to control and maintain the food temperatures. These mechanical controls tend to have an undesirable degree of inaccuracy and have a tendency to dry out food, overheat, have large swings in temperature ranges from a desired set point, which results in over and under shoots.
The sensors used in conventional warmer drawers to detect the temperature within the drawer have been mostly capillary tubes. Expanding gases, as temperature increases or decreases, transfers force or relaxes force to a mechanical switch, causing the switch to close or open, thus supplying current to or turning off current to the cal rod (i.e. sheathed heating element). The response time for these types of controls tends to be slow and also contributes to (or exacerbates) over and under shoots in temperature within the warmer drawer.
These sensors and the design of operation generally causes slow response for temperature corrections, thus causing temperatures to over shoot and under shoot. These resulting temperature ranges and swings, from the on to off cycling, have a tendency to drive moisture out of foods, hold more moisture in the chamber, and/or over cook food(s). Also, when set for the proofing temperature, bread will not proof correctly (i.e. not to rise properly) at lower temperatures, and at the higher temperatures bread tends to develop large pockets of air.
Conventional warmer drawer design typically locate the heating elements on the inside top or bottom of the chamber (e.g. box, cavity, compartment). A cal rod (sheathed heating element) used in varying patterns, provides radiant heat. This radiant heat often produces hot spots when placing an object like a pan or plate in close proximity to the cal rod. Temperature hot spots are understood to be due to the radiant heat source being strongest (hottest) near the cal rod and decreasing in temperature as distance increases away from the cal rod. Accordingly, such conventional warmer drawer designs provide undesirable temperature level variation within the chamber. These temperatures variations tend to cause problems for controlling and maintaining the food temperatures, such as stratifying or layering of air temperatures which causes problems for food holding. Also, start-up times to get warm temperatures in the chamber can be long due in part to the cal rod design. Such long start-up times are undesirable and prevent an operator from just turning the warmer drawer on and placing food in the chamber. Accordingly, such conventional warmer drawers have undesirably long start-up or pre-heat times necessary in order to stabilize the temperature inside the cavity at a desired level, otherwise food is held at lower temperatures, which can cool foods or encourage spoilage. Also as the temperature and heat cycles, large temperature over and under shoots tend to be created causing food to dry out, and loss of accurate temperature control for longer periods, and poor food holding capability.
Conventional warmer drawer designs typically use knobs and slides to set and control mechanical switches for setting the desired temperature. However, these mechanical switches are generally known to be inaccurate in their setting and repeatability. The mechanical switches often have problems maintaining a set point and can permit swings in temperature within the chamber partly due to the design of the warmer drawer and method of heating, but also due to the inaccuracy of the mechanical switches themselves. Mechanical control switches have a known condition of hysteresis, which contributes to their inaccuracy in the controllability to obtain a set temperature point or repeat a function. This inaccuracy can be demonstrated (for example) by turning the control to the right and stopping at a set point versus turning the same mechanical control past the set point and then turning the control to the left and stopping at the set point. Both actions end with the same set point selected but the resulting temperature will usually be different. The inaccuracy of the mechanical switches tends to increase the effects of having temperature over and under shoots and contributes to the large temperature swings inside the chamber of the warmer drawer. This inaccuracy is believed to contribute greatly to the gradiant temperature problems found in present warmer drawers with the chamber having problems with temperature over shoot and under shoot.
The mechanical switches typically used in conventional warmer drawers are also susceptible to the adverse effects of surrounding environmental influences. For example, if subjected to cold temperatures, mechanical switches could work slowly, crack, become hard to turn, fail to operate, their lubrication can harden causing the operation not to function, cause switch chatter resulting in premature failure or reduced life of product, and cause other detrimental issues to a user. By further way of example, if subjected to hot temperatures mechanical switches could experience slow operation from drying out of lubrication, crack, discolor, become hard to turn, fail to operate, experience switch chatter and/or premature failure, and cause other detrimental issues to a user when trying to set the controls or operate the warmer drawer. Further, if mechanical switches and/or controls are subject to outdoor environments like rain, snow, sun, UV, or the like, then special protected control switches are usually required to prevent intrusion of these environmental contaminants that may otherwise cause premature failure or reduced product life. Special sealed controls used in such environments tends to increase the price of a warmer drawer. Accordingly, mechanical switches and controls when used outdoors in conventional warmer drawers tend to create additional drawbacks such as needing to be covered or otherwise protected from the environment, which tends to increase the cost for such products.
Typical mechanical switches and controls for conventional warmer drawers tend to have poor repeatability and generally do not provide the user the ability to repeatably return to a certain preset position (e.g. reuse of same settings, etc.) or reliably establish the same temperature when using the conventional warmer drawer in a series of different operations. For example, a user generally cannot set a proper temperature on one day and then return the next day to the same set point if the controls were moved during an intervening period (as is often necessary). Temperature swings of as much as 30 degrees or more are believed to occur in such instances.
The conventional warmer drawers are also subject to other deficiencies. For example, conventional warmer drawers are typically constructed for use in permanent (e.g. built-in, etc.) installations, such as to cabinetry, an appliance, or some other generally stationary structure. Examples include conventional warmer drawers built into a cabinet under a product such as a cook top, oven, or some other appliance like a slide-in stove to a drop-in range. In other applications, conventional warmer drawers can be used in a location independently, but are still typically built into a cabinet or some structural frame. This limits the mobility of the warmer drawer from being used in a variety of desirable locations. Accordingly, it would be desirable to provide a warmer drawer capable of being used as a freestanding unit, as a mobile unit, used under a cabinet (e.g. suspended), or in areas with or without the support from a structural frame.
Therefore a need exists for a warmer drawer in which more accurate and controlled heating of objects such as food is accomplished. There also exists the need for an accurate method of controlling the operations and settings of the warmer drawer. There also exists a need for the controls of the warmer drawer to be less susceptible to environmental influences. There also exists a need for a display device to permit a user to be able to view/see the operation, temperature indication(s), set point functions, and view of the contents of the chamber. There also exists a need for a warmer drawer capable of remote control operation. There is a further need to accurately apply and control heat within the chamber of the warming drawer. There is also needed for a warmer drawer such that it can be used in any desirable location to suit the particular needs of a user.
Accordingly, it would be desirable to provide a warming apparatus, such as a warmer drawer having electronic control, with any one or more of these or other advantageous features.